The fixed plate usually has two water inlet holes respectively joining two separate pipes for hot and cold water and one hole for the outlet of the water towards the mouth of a delivery tap to which the mixer valve is applied.
As far as the movable plate is concerned, it is operated through a control rod and has a mixing chamber designed to selectively join one or both the water inlet holes with the water outlet hole.
However, the shape of the holes or openings in the overlapping plates in units available at present do not contribute to reaching optimum capacity and mixing conditions of the water unless plates are of a relatively large diameter, in order that they can have wide holes. This results in that it is not possible to maintain the cartridge-type valve at the desired size.